Spark plasma sintering of silicon carbide-nanostructured ferritic alloy composites with chromium carbide barrier layer

Abstract

Silicon carbide and nanostructured ferritic alloy (SiC-NFA) composites are expected to be remarkable candidates for nuclear cladding materials. However, SiC and NFA reactions during sintering have been a challenging problem to address. A Cr3C2 coating on SiC particles is introduced as a reaction barrier layer to fabricate novel Cr3C2@SiC-NFA composites in this work. The composites of 5vol% Cr3C2@SiC-95vol% NFA, 15vol% Cr3C2@SiC-85vol% NFA, and 25vol% Cr3C2@SiC-75vol% NFA achieve > 96% densities under spark plasma sintering (SPS) at 950°C and have the Vickers hardness of 5–6GPa. The main phase for the composites maintains the original α-Fe structure of the NFA composition. Although the NFA matrix with silicon diffusion and carbon-rich aggregates are detected, the much improved microstructures in the composites indicate the positive effects of the Cr3C2 coating as the reaction barrier. The Cr3C2@SiC-NFA composites are expected to be promising cladding materials in harsh nuclear environments.